Rigid foam panels are currently available for use as an insulating underlayment in roof construction. Typically these are 4′ by 8′ (1.22 m by 2.44 m) panels 1.5″ (3.8 cm) thick made of a 1.6 pound per cubic foot polyurethane foam with a tar paper top layer. Such a material is not crush resistant enough to be used as a roof surface material and can also be easily punctured.